Roller mounted vacuum cleaner for propulsion by flexible hose



March 24, 1953 E. P. SENNE 2,632,524

ROLLER MOUNTED VACUUM CLEANER FOR PROPULSION BY FLEXIBLE HOSE Filed May 22, 1947 5 Sheets-Sheet 1 dtzvrneys March 24, 1953 E. P. SENNE' ROLLER MOUNTED VACUUM CLEANER FOR PROPULSION BY FLEXIBLE HOSE 3 Sheets-Sheet 2 Filed May 22, 1947 INVENTOR.

m WW WA March 24, 1953 2,632,524

E. P. SENNE ROLLER MOUNTED VACUUM CLEANER FOR PROPULSION BY FLEXIBLE HOSE Filed May 22. 1947 3 SheetsSheet 3 JNVENTQR.

Patented Mar. 24, 1953 UNITED STATES PATENT OFFICE ROLLER MOUNTED VACUUM CLEANER FOR PROPULSION BY FLEXIBLE HOSE This invention relates to vacuum cleaners. The present application is a continuation-in-part of my copending application Serial No. 702,389, filed October 10, 1946, now abandoned.

The principal objects of the present invention are to provide a vacuum cleaner (of the flexible hose type) which is compact and easily maneuverable; which will roll easily over floor obstructions; which can be readily pushed, pulled or revolved by manipulation of the hose; which possesses an inherent self-leveling feature cooperative with a particular positioning of the hose attachment fixtures to keep the point of hose attachment approximately in the horizontal plane containing the axis of the wheels; which may in addition possess an electrical switch controlling the motor circuit which is actuated by contact with the floor when the chassis is rocked on its main axis; in which the suction and blowing attachments are located at or about the level of the wheel-axis so that the machine has easy handling characteristics whether it is being used for suction or blowing; in which the heaviest elements of the machine (namely, the motor elements) are positioned immediately below the wheel-axis so as to afford the self-leveling feature; and in which the motor-fan unit is readily accessible for repair without removing it from the chassis.

In the following description, and in the accompanying drawings, there is shown one form of machine embodying the present invention, which has been found to possess the particular advantages pointed out, and is set forth to illustrate the invention. The invention is not, however, confined to any particular detail of form, shape or mechanism, except as pointed out in the annexed claims.

Referring to the annexed drawings which form part of this specification:

Fig. 1 illustrates the operation of raising the hose in order to rock the chassis upon its supporting axis and thus to actuate the switch by contact with the floor.

Fig. 2 illustrates the use of the machine when it is behind the operator and is to be pulled forward by the hose.

Fig. 3 illustrates the use of the machine when it is in front of the operator and is to be rolled backwardly using the hose as a means of transmitting thrust to the machine.

Fig. 4 illustrates the use of the hose to rotate the machine in a horizontal plane (i. e., about axes normal to the floor) by means of a twist of the hose.

Fig. 5 is a vertical section through the center of the machine in the plane 5-5 of Fig. 6.

Fig. 6 is a vertical section through the machine in the plane 6-45 of Fig. 5.

Fig. 7 is a partial vertical longitudinal elevation, partly in section, of the chassis with one wheel removed, showing the chassi in rocked position when the switch plunger 10 is about to come in contact with the floor.

Fig. 8 is a vertical transverse section through the removable intake unit 30 in the plane 8-8 of Fig. 5.

Fig. 9 is similar to Fig. 5, showing the hose attached in the exhaust receptacle so that the machine is suited for use as a blower.

This invention relates chiefly to vacuum cleaners of the type often referred to as the flexible-hose type which consists of three principal parts: a cleaning unit [5 which contains the dirt-filtering bag, fan and motor; a flexible hose 5?; and a wand 58 usually of steel or other stifi material which has appropriate attachments for suction cleaning or for blowing, spraying, and the like.

According to one embodiment of the present invention, the cleaning unit consists of a chassis i5, having two large supporting wheels I3 and. I4 mounted on the end of a shaft which protrudes on either side of the chassis. These Wheels are domed outwardly on either side of the chassis, and the annular shell of the chassis, between the wheels, is correspondingly rounded so that, with the exceptions to be noted below, the entire unit presents the appearance of a sphere. This configuration aiiords a pleasing appearance. The dome-shaped wheels tend to prevent interference with furniture, rugs and other obstructions. Wheels I3 and 14 have annular rim portions 18 projecting outwardly of the spherical surface and terminating in circular treads l2.

Chassis The chassis, indicated generally by the reference numeral [5, consists of two flat side plates of circular outline l6 and I1 spaced apart in parallel planes sufficiently to provide space between them for the dirt-filtering bag and the motor-fan unit. The distance between these plates, in the device shown, approximately equals the distance which separates the inner edges of treads 12. The annular edge of each plate extends beyond the shell member l8 (about to be described) and almost, but not quite, to the diameters of the treads 12.

A curved shell l8 secured along its edges to side plates l 3 and fl is suitably shaped according to the spherical outline previously mentioned and with the side plates l3 and IT forms an enclosure for the chassis 15. Within this enclosure a horizontal separating plate i9 is suitably secured along its edges to the side plates [6, ll and to the shell it in such manner as to divide the enclosed space into upper and lower compartments.

A transverse fixed shaft 29, substantially in the plane of plate I9, passes through side plates l6 and it at about the center of each of them. Laterally extending end portions 2| and 22 of shaft provide bearings on which the hubs 23, 2. 3 of wheels 13, M are respectively journalled and secured. Preferabl the hubs are secured upon these shaft ends by means of screws 25, 28 which may be removed for removal of the wheels.

Separating plate [3 is provided with an upwardly projecting transverse ridge 2'! whose lower concave side seats upon shaft 20. 'Ihis ridge and side plates iii and Il transmit the weight of the chassis to the shaft 23 by which it is supported in such manner as to be capable of rocking upon the shaft under the gravitational influences mentioned below.

The enclosed space within shell 18 above separating plate 13 is herein described as the dirt chamber 28. The forwardend of this chamber (theleft as seen in Fig. 5) provides an opening defin'ejd'by the intu'rned edge 29 of shell it. Ihis opening is adapted to receive a removable intake unit 33 (see Fig. 8). Intake unit 36 is manually removable, and may be locked in place. It serves the dual functions of receiving the locking fixture I I on the end of the flexible hose 5? and of holding in place, within chamber 28, a dirt-filtering bag. Intake unit 30 is formed of ashell member 3! shaped to conform generally to the spherical outline of'the entire device, and a wall member 32 adapted to engage'the inturned'edge 29 of shell iii. In the lower portion of intake unit 33 is'formed a receptacle 33 for receiving (and securing in any known manner) the locking fixture H. An annular rim 34 secured to wall member 32 providesa recessed annular channel adapted to secure the metallic rim 3 5 'of a dirt-filtering bag 35. Bag 36 is secured to rim 3 5 in the usual manner. Separating plate I 9 is provided with a curved depression 31 adapted to be engaged by the lower part of [the rim'35 when the bag is in position.

' Intake unit 3E} is adaptedto be secured in place by means of a locking mechanism 'operatedby a single control lever. This mechanism comprises a locking handle 38 pivoted at 39 and having a wedge-shaped lug 40 (see Fig. 8) adapted to be inserted between the opposed ends of two alined locking bars M, 42 slidably secured' by screws 43; M to one face of wallmember 32. The screws pass through slots 45, in bars MAZand sufficient play is provided to permit free movement of bars ll, 42 in a direction transverse to the device as a whole. Springs 4.7, 43, each secured at one of its ends to wall member 32 and atthe other of its ends to bars H and 62, urge these bars to move toward each other. When the locking handle is moved (in a clockwise direction as seen in Fig. 5)- to the closed position shown in Fig. 5, the pointed end of lug 4E! enters between the ends of bars 4! and 42, which are appropriatelybeveled to facilitate its entrance. In this way locking bars i I, 42 are moved outwardly (see Fig. 8) and their out- 'ward extremities penetrate openings iii, 50. in the side plates It, ll, respectively. Engagement of the ends of bars 4|, lzwith the openings 49, 5t

looks intake unit 39 in the position shown in Fig. 5. counterclockwise rotation (as seen in Fig. 5) of locking handle 38 about its pivot 39 retracts the nose of lug ill, permits the springs to retract locking bars ll, 52 from engagement with openings 49, 50, and thus frees intake unit 30 for removal from the machine. A spring 5| secured to lockinghandle 38. and bearing against the inner surface of shell member is reversely curved in such manner as to urge handle 38 either in the direction of its open position as it approaches open position, or in the direction of its closed position as it approaches closed position, or both, thus affording a snap action opposing movement of the handle and securing it in the position to which it is moved.

When it is desired to insert a fresh bag in chamber 28, intake unit 3%? is unlocked and manually removed, permitting the old dirt-filled bag to be removed. The rim 35 of this bag is thereupon disengaged from annular rim 34 of the intake unit and the bag is either thrown away (if replacement by a fresh bag is contemplated) or its contents are emptied. 'Ihereupon the metal rim 35 of an empty bag is engaged within annular rim 3d and the bag is reinserted in chamber 28 in such manner that the lower portion of the bag rim 35 is pressed against the wallof the depression 3'! in the separating plate i9. Intake unit 30 is then locked in position in the manner indicated.

The lower chamber 50 within chassis 15 beneath separating plate It contains a fan 52 and motor 53 of conventional construction. Normally the fan and motor are formed as a single motor.- fan unit which is bolted to the flanges of an annular plate 54 secured to separating plate 19 and the lowermost portion of shell l8. Motor-fan unit 52, 53 is arranged to draw air from the rearward end of the chassis (the right-hand end as seen in Fig. 5 and to deliver it towards the, front end of the chassis (the left-hand endas seen in Fig. 5). To accommodate the passage of air from the upper to the lower chambers, there is provided a series of holes 55 formed in the separating plate 19 adjacent the intake end of the motorfan unit. Air propelled by the motor-fan unit leaves the lower chamber as set forth below.

Immediately below receptacle 33 is. positioned a second receptacle Hi3, preferably similar in dimensions with those of receptacle 33, affordingan air pathway between the atmospher and'the lower chamber. Receptacle I00 provides the opening through which air propelled by thefan leaves the lower chamber. Receptacle I00 is similarly dimensioned to receptacle 33 in order that locking fixture H on the end of the hose. may, optionally, be inserted in receptacle I00. if desired. When this is done, the machine is adapted for use as a blower, thefiltering bag not being used (being if desired removed). A removable perforated grille ml is adapted to be seated in receptacle I 00 when-the hose is not engaged therewith.

Receptacles 33 and Hit are each located as near as may be to that part of the periphery of the chassis which, when the chassis is level (as shown in Fig. 5), is in approximately the horizontal plane which contains the axis of the wheels l3, [4. The purpose of this arrangement is I indicated below.

Spanning a cup-shaped depression 6! in the upper surface of shell I8 is a rigid handle 62 suitably curved to conform to the spherical outline of the device as a whole and affording a.

means by which the entire cleaning unit may be picked up by hand. The handle is located approximately above the center of gravity of the chassis.

Rotatably-mounted upon one end portion 22 of shaft 20 is a spring-tensioned reel 63 having wound thereon cable 64 which connects motor 53 to a suitable source of power. The free outer end of cable 64 passes outwardly through shell [8 through a hole 65 and is provided with a plug for attachment to an outlet socket. The arrangement is such that tension is exerted on cable 64 tending to reel it up within the machine, so that slack will be taken up. Reel 63 is located externally of the chassis and is concealed within the domed recess adjacent hub 24 of wheel [4.

Accessibility for purposes of repair and adjustment is afforded through the following means. Shaft 20 has an enlarged disc portion 66 integral therewith adapted to be secured by screws 61 to the side plate It, thus securing shaft 20 against lengthwise displacement and against rotation relative to the chassis. A disc 68, loose upon shaft 20 and preferably secured to side plate I! serves as a spacer between side plate I! and reel 63 and provides a key (not shown) furnishing an abutment for the spring which tensions reel 63. Access to the interior of chassis I5 may be had by removing wheels 13 and I4, slipping reel 63 off shaft 20 (after disconnecting the wire connections), and removing the screws 61 which permit shaft 20 to be withdrawn. Thereupon the side plates IS, IT, or either of them, may be removed by removing the screws which secure it to shell 18 and plate I9, and the interior of the chassis is thus laid open at either side for inspection and repair of the parts contained in it, particularly the motor-fan unit, without dismounting these parts from the chassis.

By dividing the chassis into upper and lower compartments, one above the other, and positioning the relatively heavier motor-fan unit in the lower compartment and the relatively lighter dirt-filtering bag in the upper compartment, two effects are achieved. First, the cleaner as a whole is evenly balanced when lifted by the handle 62 and, second, the center of gravity of the chassis is positioned approximately just beneath the shaft 20. These effects are utilized for the purposes described below.

Preferably the motor-fan unit should be so disposed in chamber 60 that the center of gravity of the chassis as a whole is substantially directly below the axis of shaft 20.

Support for the chassis The projecting ends 2| and 22 of shaft afford, in the specific device here described, the sole means through which chassis l5 rests upon its supporting wheels.

I Wheels 13 and I4 consist of hubs 23 and 24, disked spokes 19 suitably curved to conform to the spherical outline, and annular rim portions 18 which extend outwardly beyond the general spherical surface. Curved surfacing material 80 is secured to the outer face of hubs 23, 24, spokes l9 and rims 18 to present a finished appearance, and treads I2 of suitable material, preferably chromium-plated steel, ar provided around the wheel peripheries. The radius of wheels [3, I4 is so arranged that the spherical underbelly of chassis I5 is supported clear of the floor by an amount of clearance 14 which is great enough to permit the cleaner to be moved freely over rugs and-other minor irregularities and is at th same time small enough to permit the switch actuating mechanism, below described, to come in contact with the floor when the chassis is rocked about its axis, i. e., shaft 20.

While the support for the chassis here shown consists of two large wheels journalled at their hubs, it is to be understood that other supporting mechanism such as a journalled shaft, rimjournalled wheels or like equivalents may be employed. In general, it is believed, easy maneuverability can be secured, through the use of my invention, when the wheel treads are of large diameter and easily rotatable.

Electrical switching mechanism Current for the motor 53 is supplied through cable 64 normally wound, as above described, on the spring-held reel 63. The inner end of this cable is connected to the terminals of switch 69, and when this switch is in closed position current is supplied (through circuits not shown) to the motor 53.

Switch 69 (see Figs. 5, 7 and 9) is preferably of the plunger type in which alternate depressions of a. plunger iii against the resistance of a spring (not shown) move the switch contacts to closed position, and intervening depressions of the plunger move the switch contacts to open position. The details of this switch are not shown in the annexed drawings, being of conventional design. The switch is mounted upon a lower portion of shell l8, approximately as shown in Fig. 9. The clearance it between the bottom of shell it and the floor level when the chassis is balanced in normal or horizontal position as indic-ated in Fig. 9, and the extent to which plunger iii normally projects outwardly from the spherical surface of shell it when the spring is extended, are so arranged that when the chassis as a whole is rocked about its pivotal point of support (the axis of shaft 28) from the position shown in Fig. 9 to and beyond the position shown in Fig. 7, plunger '53 will come in contact with the floor on which the vacuum cleaner rests, and will thereby be pressed inwardly toward the center of the sphere to an extent sufficient to actuate the switch from open to closed, or from closed to open, position. Thus, each time the chassis is rocked sufiiciently to depress plunger Iii by contact with the floor, the switch is actuated and the motor is energized or deenergized.

In order to rock chassis ii, the operator has only to lift the end of flexible hose 5'! near to its point of attachment with the machine. By so doing the chassis is tipped from its normal balanced or horizontal position, and as the hose is lifted the plunger 10 is pressed against the floor. One lift of the hose energizes the motor; a succeeding lift deenergizes it.

In my co-pending continuation-in-part application, Ser. No. 61%98, filed December 27, 1948, and entitled Vacuum Cleaner On-and-O-ff Switching Devices, 1 disclose and claim broadly mechanisms exemplified by the foregoing for alternately energizing and deenergizing vacuum cleaners of the general character herein disclosed by successive manipulations of the hose away from and return to a predetermined normal operating position to effect switch actuating relative movement of the various machine parts with respect to each other or a floor.

Mode of operation The manner in which the machine is operated 7. will, now bfi; described with. special. feren e, Rigs. 1, to 4,

When the. machine is being used to provide suction through hose the lockingattachment H for. the hoseis secured within receptacle 33; Infithe normal. balanced position, of they machine, indicated in, Fig. S thisreceptacle is positioned apprpximately. intheequatorial zone, o fjthe chassis, The machine tends to remain-in thisbalancedposition by reason or" theheavy mass ofjthe motor-fan unit. being disposed underneath shaft- 212. Any, tendency of the chassis torock from this position is opposed-by this mass, which tends constantly to keep the chassis on an even keel. Receptaclet d isso located, withreference to the center of gravity of the machine that receptacle 334s maintained ator near the-horizontal: plane containings-haft 23'. This. position is the one to which I refer-as the equatorialposition.

Thus, when thehose is attached to receptacle 33;; and the operatorseeks tomaneuver. the machine about the-floor by pushing, pulling. or whirling the hose, the point to which force-is thereby app-lied to the machine tends always tobe at approximately the equatorial level of the chassis, abouton a levelwith (but in an axis at right angles to) the main shaft 2Q.

This relationship produces several functional advantages which arebelieved not to have been realized in priormachines. Whenthe machine is pushed by means of the hose (see Fig. 3), it does not roll over" but keeps itself in such position that it receives the thrust imparted to it through the hose at about the level of the shaft, and responds to it by movingaiong the floor with the chassis remaining level and the wheels revolving in a direction away from the operator. When themachine has come into interference with furniture or rugs, or the hose has become twisted, a quicktwirl of the hose by the operator (see Fig. 4) will -cause the machine-as whole to pivot on its two wheels (1. e. about axes normal to the floor) soasto resume a position where it can be directly pushedor pulled by the hose, and without tending to roll-over on its back. Thus the machine remains highly maneuverable at all times. Also the pickup handle is kept always on top.

Furthermore, the operator is relieved of the necessity of leaning over to operate the switch when-it is desired to-shut oif the motor temporarily. By merely'raising the hose (see Fig. 1) the chassis is rocked about shaft 28 till plunger Wis-depressed bycontact with the floor and the motor circuit is thereby opened. By repeating this action, the motor circuit is again energized.

The importance of the self-levelingfunction of the machine, and of the easy-rolling characteristics imparted to it by the two large wheels; is emphasized bythe comparatively weak thrust which can be imparted through the hose. The hose used in such machines is characteristically very flexible and possesses little resistance to bending. In order that so flexible a means shall be useful in pushing the machine away from the operator (as shown in Fig. 3) itis-essential that the-point ofattachment of the hose, shall not easily rotate to the top of the machine.v The selfeleveling feature above-described opposes such action.

Further, by locating the receptacle it as near as maybe inthe same equatorial region of the chassis (i. e., close to thehorizontal plane which, when the chassis is level, contains the axis on which the wheels are pivoted), the machine is likewise easily responsive andmaneuverable when being used as a blower. In thiscasdas set forth abo ve, the hose is attached; in receptacle I 00; thefan exhaust port: Byarranging this port, as well, near the equatorial-region, themachine canbe handled in the same easy fashion when used as a blower.-

When the machine-is used; as'a blower; any of the known attachments maybeemployed on the endof the wand 58".

attachmentv I32 may be provided. When the machine is usedas a-blower; thedirt -filteringbag 28' is preferably removed;

Since the means by which: locking fixture H may be removablysecuredwithin receptacle 33' arewell-known, I donot describethem in detail; A similar arrangement is contemplated withrespect to receptacle I00.

Angular: relationships,

Since, as pointed out above; ease of maneuver.- ability is dependent on assuring that the'hosewill' ordinarily be maintained. approximately in they equatorial region of the sphere, andthis depends on the action of gravity acting upon the center of mass of" the apparatus disposed within case. i5; it ispointed out as follows:

The center of mass should be asubstantiatdisrtance removed from. the. axis of 1 support of; the. case. The further removed ltriS; the-.-more.pro:- nounced will be thetendency' of the case;=.to; ire-.- gain its normal position after being disturbed. Practical limitations of design, however, make it impossible to remove the centerxofzmass:more than a few inches below. shaft 28: In 1Fig..9;the

point its is assumed to representathe; center of mass of the case and-contents This point; when the case has rocked :itself' to normal position, lies on the radius ind extending downwardly. from shaft Under these conditions .a'secondradius Hi3 may be regarded as the. radiusanearrwhich (approximately): the hose attachmentsockets, -33 and lot .lie. A' third radius I ;.may; beregarded as the radius. in which theflooii-contact switch fifi ispositioned. Ideally radii I03 landj Dil -should be at right'angles .to .eachother; Radii,:,l04r and ltit may be at any desired an le,but:for;greatest. convenience-should be. an acuteangle; (i. e., less than,90) and are.shownyatanxangle-otapproximately.609.- These-radiiaretaken in a plane at right angles to the axis'offshaftiils; i. e.,,the axis :of support.

The position oi hose attachmentsockets133and i9 5) may. be. varied .withina. considerable -ang ular range as seen in Fig. 9. Generally speaking. these sockets should be located at a point remote from the vertical'plane containingshaft 20 and radius it'd. Furthermore, in ordertosecuremaximum ease of maneuverability, the axis of these sockets should be aimed more or less in the di rection of shaft 29, and shouldbe.approximately midway between the twowheels.v (see Fig.1).

Wherereference is madehereintoa dirtfiltering bag, it isintended that the reference shall be understood to include bags vof any type useful ,for. thepurpose, whether. of. cloth, .Daper or other material, and, in addition, filtering 61G:- ments other thantrue bagswhich may be, suitable for thepurpose. Theinvention .is. not lim: ited :to any particular.shape or configuration .of parts, nor specifically; to the spherical shape of the cleaner unit here-shown to illustratetheinv vention, but-is'to be-takenas including. any de: vice embraced within 1 the-following, claims.

1.. .An: air filter machine adapted tobe pushed.

For-example, if theblowing is to be utilized for spraying, a suitable-sprayingpulled or rotated on a floor by manual forces exerted on a flexible cleaning hose, comprising a chassis containing a dirt filter and an air propulsion mechanism for propelling air through said filter, means supporting said chassis clear of a floor for self-leveling rotation about a substantially horizontal axis of rotation, said supporting means including a wheel mechanism adapted to support said chassis for free rolling movement over a floor and for rotation about axes normal to the floor, means on said chassis adapted for the attachment of a flexible hose, said axis of rotation being displaced substantially from the center of gravity of said chassis whereby said chassis will normally assume an equilibrium self-leveling position under the influence of gravitational forces and whereby its stability in such position is suflicient to enable said machine to be pushed and rotated about said axes normal to a floor by manual forces exerted on such a hose without substantial departure of said chassis from said equilibrium position, said means for the attachment of a hose being so positioned that radii drawn from said axis of rotation to said means, and to said center of gravity, are approximately normal to each other whereby pushing forces exerted on such a hose will tend to have a minimum moment of rotation about said axis.

2. An air filter machine adapted to be pushed, pulled or rotated on a floor by manual forces exerted on a flexible cleaning hose, comprising a chassis containing a dirt filter, means supporting said chassis clear of a floor for self-leveling rotation about a substantially horizontal axis of rotation, said supporting means including a wheel and axle mechanism mounted coaxially with said axis of rotation and adapted to support said chassis also for free rolling movement over a floor and for rotation about axes normal to the floor, means on said chassis adapted for the attachment of a flexible hose with one end thereof aligned to direct air to said filter, an air propulsion motor-fan unit located within said chassis below said axis of rotation and of such weight as to place the center of gravity of said chassis substantially away from said axis whereby said chassis will normally assume an equilibrium selfleveling position under the influence of gravitational forces and whereby its stability in such position is suflicient to enable said machine to be pushed and rotated about said axes normal to such a floor by manual forces exerted on said hose without substantial departure of said chassis from said equilibrium position, said means for the attachment of a hose being so positioned that radii drawn from said axis of rotation to said means, and to said center of gravity, are approximately normal to each other whereby pushing forces exerted on such a hose will tend to have a minimum moment of rotation about said axis.

3. An air filter machine adapted to be pushed, pulled or rotated on a floor by manual forces exerted on a flexible cleaning hose, comprising a chassis, means Supporting said chassis clear of a floor for self-leveling rotation about a horizontal axis of rotation, said supporting means including an axle and wheels mounted thereon on opposite sides of said chassis and coaxially with said axis of rotation whereby said means are adapted to support said chassis also for free rolling movement over a floor and for rotation about vertical axes normal to said axle, a dirt filter located within said chassis above said axis of rotation, means on said chassis adapted for the attachment of a flexible hose with one end thereof aligned to direct air to said filter, and an air propulsion motor-fan unit located within said chassis below said axis of rotation and of such weight as to place the center of gravity of said chassis substantially away from said axis whereby said chassis will normally assume an equilibrium self-leveling position under the influence of gravitational forces and whereby its stability in such position is sufficient to enable said machine to be pushed and rotated about said axes normal to said axle by manual forces exerted on such a hose without substantial departure of said chassis from said equilibrium position, said means for the attachment of a hose being so positioned as to be approximately in the horizontal plane containing said axis of rotation when said chassis is in said equilibrium position whereby pushing forces exerted on such a hose in a horizontal direction will tend to have a minimum moment of rotation about said axis.

4. An air filter machine adapted to be pushed, pulled or rotated on a floor by manual forces exerted on a flexible cleaning hose, comprising a chassis containing a dirt filter mechanism and an air propulsion mechanism for propelling air through said filter mechanism, a pair of wheels and an interconnecting axle supporting said chassis clear of a floor for self-leveling rotation about the axle, and means in said machine adapted for the attachment of a flexible hose, the axle being displaced substantially from the center of mass of said chassis whereby the chassis will normally assume an equilibrium self-leveling position under the influence of gravitational forces and whereby its stability in such position is sufficient to enable said machine to be pushed and rotated about a floor by manual forces exerted on such a hose without substantial departure of said chassis from said equilibrium position, said means for the attachment of a hose being positioned substantially in a plane containing the axle, which plane is normal to the plane of the axle and center of mass of the chassis, whereby pushing thrusts on such a hose are applied to said machine substantially only in planes through said axle whereby rotation of said chassis about the axle by said thrusts is minimized.

5. An air filter machine adapted to be pushed, pulled or rotated on a floor by manual forces exerted on a flexible cleaning hose, comprising a chassis containing a dirt filter mechanism, a pair of wheels and an interconnecting axle supporting said chassis clear of a floor for self-leveling rotation about the axle, means in said machine adapted for the attachment of a flexible hose with one end thereof aligned to direct air to said filter mechanism, and an air propulsion motor-fan unit located within said chassis below said axle and of such weight as to place the center of mass of said chassis substantially away from the axle whereby said chassis will normally assume an equilibrium self-leveling position under the influence of gravitational forces and whereby its stability in such position is sufiicient to enable said machine to be pushed and rotated about a floor by manual forces exerted on such a hose without substantial departure of said chassis from said equilibrium position, said means for the attachment of a hose being positioned substantially in a plane containing the axle, which plane is normal to the plane of the axle and center of mass of the chassis, whereby pushing thrusts on such a hose are applied to said machine substantially only in planes through said axis whereby rotation of ll said chassis about the axle by said thrusts is minimized.

6. An air filter machine adapted to be pushed, pulled or rotated on a floor by-manual .forces exerted on a flexible cleaning hose, comprising 'a chassis, a pair of wheels and an interconnecting axle supporting said chassis clear of a floor for self-leveling rotation about said axle, 'a dirt filter compartment located within said chassis on one side of said axle, means in said machine adapted for the attachment of a flexible hose with one end thereof aligned to direct air to said filter compartment, and an air propulsion motor-fan unit located within said chassis on the other-side of said axle and of such weight that said chassis will normally assume an equilibrium self-leveling position under the influence of gravitational forces in which position the filter compartment is above and the motor-fan unit below the axle,

the motor fan unit also being of such Weight that the stability of the chassis in such position is sufficient to enable said machine to be pushed and rotated on a floor by manual forces exerted on such a hose without substantial departure of said chassis from said equilibrium position, said means for the attachment of a hose being positioned substantially in a plane containing the axle, which plane is normal to the plane of the axle and center of gravity of the :chassis, whereby pushing thrusts on such a hose are applied to said machine substantially only in planes through said axis whereby rotation of said chassis about the axle by said thrusts is minimized.

EDGAR P. SE-NNE.

REFERENCES CITED The following references 'are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 521,868 Shay June 26, 1894 952,681 Matheson Mar. 22, 1910 1,184,574 Schlesinger May 23, 1916 1,247,907 Tully Nov. 27, 1917 1,573,771 McClatchie Feb. 16, 1926 1,655,746 Wachtel Jan. 10, 1928 1,856,133 .McClatchie May 3, 1932 2,231,326 Dow Feb. 11, 1941 2,550,384 Senne M Apr. 24, 1951 FOREIGN PATENTS Number Country Date 107,187 Austria Sept. 10, 1927 355,06 Great Britain Aug. 20, 1931 464,480 Germany Aug. 31., 1928 

